Field of the Invention:
The present invention relates to a substrate cleaning apparatus and a substrate cleaning method for cleaning a surface of a substrate, such as a semiconductor wafer, and more particularly to a substrate cleaning apparatus and a substrate cleaning method for use in a substrate cleaning process for cleaning a substrate surface after a polishing process, such as CMP. The substrate cleaning apparatus and the substrate cleaning method of the present invention can also be applied to a cleaning process in manufacturing a flat panel, an image sensor, such as CMOS or CCD, and a magnetic film of an MRAM.
Description of the Related Art:
A damascene interconnect forming process is a process of forming interconnects by filling a metal into interconnect trenches formed in a dielectric film on a substrate surface. After the formation of the interconnects, an excessive metal on the substrate surface is removed by chemical mechanical polishing (CMP). Residues of slurry, polishing debris, etc. are present on the substrate surface after CMP. Therefore, it is necessary to remove such residues (particles), remaining on the substrate surface after CMP, and metal impurities formed on the substrate surface.
An SC-1 cleaning process (or Standard Clean 1), which is intended to mainly remove particles, is known as a substrate cleaning method of cleaning a substrate surface that has been subjected to the CMP. This SC-1 cleaning process uses a cleaning liquid (an SC-1 cleaning liquid) comprising ammonia water and a hydrogen peroxide solution diluted with pure water to a predetermined concentration. Further, an SC-2 cleaning process (or Standard Clean 2), which is intended to mainly remove metal impurities, is known. This SC-2 cleaning process uses a cleaning liquid (an SC-2 cleaning liquid) comprising hydrochloric acid and a hydrogen peroxide solution diluted with pure water to a predetermined concentration.
In an example, when carrying out the SC-1 cleaning process, pure water, ammonia water and a hydrogen peroxide solution are stored in a tank at a predetermined ratio, and the cleaning liquid in the tank is supplied to a substrate by a pump while agitating the cleaning liquid by means of a pump or an agitating plate so as to uniformly mix the pure water, the ammonia water and the hydrogen peroxide solution.
However, such a so-called “tank method” that employs a tank for storing a cleaning liquid, not only needs an installation space for the tank which generally has a large volume, but also needs pipes that connect the tank with processing liquid supply sources, pumps for pumping processing liquids, and other equipment, thus requiring use of a complicated large-scale apparatus.
An in-line substrate cleaning method, which does not use such a tank, has been proposed. For example, Japanese Laid-Open Patent Publication No. 2001-338903 discloses a method which involves supplying a liquid mixture (cleaning liquid), comprising a mixture of a plurality of processing liquids (NH4OH, H2O2 and pure water), to a substrate to process the substrate. In this method, the processing liquids are supplied to a substrate in such an order as to cause less damage to the substrate, e.g., in the order of pure water, H2O2 and NH4OH. Further, Japanese Laid-Open Patent Publication No. 2008-277576 discloses a substrate cleaning method in which a cleaning liquid is produced by diluting a liquid mixture, comprising ammonia water or hydrochloric acid and a hydrogen peroxide solution, with pure water, and the cleaning liquid is supplied directly to a substrate.
When cleaning a substrate surface by supplying the cleaning liquid (the SC-1 cleaning liquid) comprising ammonia water and a hydrogen peroxide solution, diluted with pure water to a predetermined concentration, to the substrate surface, it is preferred in the light of uniform processing (cleaning) to use a cleaning liquid in which pure water, ammonia water and a hydrogen peroxide solution are kept uniformly mixed at a constant ratio, and to continuously supply such a cleaning liquid to the substrate from the start of the cleaning process. If there is a difference in the concentration of component, e.g., hydrogen peroxide solution, in the cleaning liquid, a reaction mark may be produced on the substrate.
However, it has been generally difficult in the in-line cleaning method to continuously supply a cleaning liquid, comprising pure water, ammonia water and a hydrogen peroxide solution, to a substrate while keeping the components of the cleaning liquid uniformly mixed at a constant ratio from the start of cleaning the substrate.